Step-up ring



FIG. 1 is a front perspective view of a step-up ring in accordance with the present invention;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4. is a top view thereof, the bottom view being a mirror image; and,

FIG. 5 is a side view thereof, the opposite side view being a mirror image.

The broken lines shown in the drawings depict portions of the step-up ring that form no part of the claimed design. 

CLAIM The ornamental design for a step-up ring, as shown and described. 